Process for concentrating oxidized ores by means of froth flotation



Patented Aug. 2, .1938

UNITED STATES,

, 2,125,531 PATENT OFFICE PROCESS FOR CONCENTRATING OXIDIZED ORES BYMEANS OF FROTH FLOTATION Grgoire Gutzeit, Geneva, Switzerland, assignor,by mesne assignments, to Visura Treuhand Gesellschaft, Zurich,Switzerland, a corporation of Switzerland No Drawing. ApplicationFebruary 27, 1936, Se-

rial No. 66,055. In Germany March 4, 1935 The invention contemplates theuse, as pulp.

conditioning reagents, of complex hydrolyzable polyacids and, morespecifically, relates to the use of isopolyacidaor the salts thereof ofa certain group of metals whosenormal salts or acids, when incorporatedin an acid, neutral, or slightly al- 1 kaline solution, are knownto-form complex isopolyacids. r 1

Sulphide minerals generally are easily amenable' and readilylend-themselves to concentration by froth flotation through the use, asflotation reagents, of organic thio-derivatives such as the xanthates.Oxidized minerals, however, have been found to be quite refractory toxanthate flotation and attempts at the froth flotation of oxidizedvalues have been, on the whole, not very cupied by an acid radical ofthe same chemical.

nature, while a heteropolyacid is a polyacid in which the position of atleast one of the oxy atoms is occupied by an acid radical of a differentchemical nature. Certain heteropolyacids, for instance, phosphomolybdicacid and phosphotungs- 3 tic acid, have been employed in the flotationof "oxidized chrome ores, namely, in the patent to Arnold No. 2,082,817,and have shown some success.

It isan object of this invention to provide an improvement in therecovery and grade of concentrate in the froth flotation of oxidizedbase metals through the employment, as conditioning agents, of a groupof complex chemical compounds coming within the class of polyacids, andcomprising certain compounds from the group known as isopolyacids. 7 Itis discovered, asa part of this invention, that conditioning of an orepulp containing oxidized base metal values in the presence of one ormore isopolyacids of metals from the group comprising tin, tungsten,vanadium, molybdenum and germanium, and then subjecting the pulp to:froth flotation by the addition of conventional frothing and collectingreagents, renders. these oxidized valuesreadily amenable to flotation ina concentrate of rich grade. The activating effect of 'hese isopolyacidsis believed to be due to the fact so that, after hydrolysis has takenplace, semicol- 8 Claims. (01. 209-166) loidal, high molecular systemsare adsorbed on I V the surface of the ore particles, thus forming apolar film which allows the combination with the collector.

Additions of reagents to the ore pulp in order to insure the presencetherein of the desired isopolyacids may be made in several ways. In oneinstance a salt of an isopolyacid of the metals from the groupheretofore mentioned, may be added directly to the pulp, therebyinsuring the presence of the isopolyacid or itssalt in the pulp.

In another instance, the normal salt 'or the normal acid of metals fromthe group mentioned, may be introduced to the acid, neutral, or slightlyalkaline pulp and, when so introduced, will form in solution, theisopolyacid of the particular metal used.

Jander and Jahr in Kolloid. Beihefte, Band 41, pages 1-58, have proventhat when the normal salts or acids of the metals, tin, vanadium,molybdenum, tungsten and germanium, are dissolved in acid, neutral orslightly alkaline solutions, they do not behave as do other metals butclearly form their respective complex isopolyacids. Therefore, in orderto insure the presence in the pulp of the desired isopolyacid, all thatis neecssary is to introduce into the pulp, while it is in acid, neutralor slightly alkaline condition, a normal salt or normal acid of a metalfrom the group aforementioned. According to an embodiment of theinvention, at least one isopolyacid of a metal of the group mentioned iscaused to exist in the pulp.

There will be hydrolysis which can be strengthened by means of weak acidor alkaline reagents. Then there must be allowed suflicient time, whichcan only be determined empirically, for the oxidized values to becomethoroughly conditioned by the isopolyacid reagent. Then flotation of thethus conditioned oxidized values is efiected in known manner, preferablywith the addition of gang-ue depressing agents, a collector and afrothing agent. The pulp temperature, the concentration of hydrogenions, and the duration of treat--, ment are to be determined in eachinstance for the particular ore.

Proceeding in this manner, it will be possible- The working of thisprocess is set forth by the following examples, which, of course, arenot meant to be limiting in any way.

1. A chromic ore (chromic iron with basic serpentine gangue) is wetcrushed to 100 mesh (U. S. A. standard). After thickening to a ratio of122-, the pulp is brought into a suitable conditioning tank and slightlyalkalized with sodium carbonate, whereupon 0.5 kg. of ammonium molybdateis added. This salt has the formula: (NH4)6M07024.4H2O and is thereforean isopolyacid salt. (See Treatise on Chemistry, Roscoe 8i Schorlemmer,MacMillan 8: Co., London, 1913, vol. 2, The Metals, page 1068.) Afterconditioning for 40 minutes, there are added 2.0 kg. of water glass (28B.) as a gangue depressing agent, 1.0 .kg. oleic acid and 0.2 kg.phosphocresylic acid per ton of pulp. Finally,- minutes oiling andfloating with 0.02 kg. pine oil, a frothing agent. As a result there isobtained a concentrate showing 58 to 60% chromic .(U. S. A. standard)and conditioned. To the pulp is then added 0.1 kg. of sodium stannateand 0.3 kg. sodium vanadate per ton of pulp. Since the pH of the pulpwill naturally be not more than slightly alkaline, the addition of thesenormal salts will cause the formation in solution of the isopolyacids oftin and vanadium, as-

previously described. After a suitable condi-' tioning period the pulpis treated with 2.5 kg. quebracho bark, in order to depress the gangue.Finally, floating is done at 35 C., (95 F. with 0.75 kg. of stearicacidand 0.05 kg. of amyl xanthate, as collectors, and 0.03 kg.terpin'oil, as a frothing agent. I

3. A tin ore cassiterite (with schist gangue) is wet crushed to minus 65mesh (U. S. A. standard). After thickening, 0.02 kg. of sulphuric acidand 0.6 kg. of tungstic acid per ton of pulp are added. In solution inthis pulp the tungstic acid will naturally form the isopolyacid oftungsten as hereinbefore shown. After 25 minutes conditioning in thepresence of the isopolyacid of tungsten at 30 C. (86 F.) floating ensuesin the usual way with 1.2- kg. of sodium palmitate and 0.03 kg. ofcresol to the ton.

Thus, in the flrst example, a. salt of the isopolyacid of molybdenum isadded directly to the ore pulp and the pulp conditioned in the presenceof this isopolyacid. In the second example, the normal salts of tin andof vanadium are added toithe pulp, resulting in the formation,-

in solution, of the isopolyacids of these two metals so that the pulp isconditioned in their presence. Example 3 shows the addition to the pulpof tungstic acid which, in solution, forms the isopolyacid of tungstenas the advantageous conditioning agent.

The invention, therefore, has several aspects and may be accomplished indivers manner.

' An isopolyacid salt of at least one of the thorough activation of theoxidized base metal values so that they may be subsequently recovered ina flotation concentrate of high grade,

through the use of relatively small amounts of normal gangue depressing,collecting and frothing agents.

What I claim is:

1. In the concentration by froth flotation of ores containing oxidizedbase metals, the method which comprises subjecting a pulp containingsuch ores to conditioning in the presence of an isopolyacid of a metalchosen from the group consisting of tin, tungsten, vanadium, germanium,and molybdenum, and thereafter subjecting the pulp to froth flotation toobtain a concentrate rich in oxidized values.

2. In the concentration by froth flotation of ores containing oxidizedbase metals, the method which comprises subjecting a pulp containingsuch ores to conditioning in the presence of an isopolyacid ofmolybdenum, and thereafter subjecting the pulp to froth flotation toobtain a concentrate rich in oxidized values. I

3. In the concentration by froth flotation 0f ores containing oxidizedbase metals, the method which comprises subjecting a pulp containingsuch ores to conditioning in the presence of an isopolyacid of tin, andthereafter subjecting the pulp to froth flotation to obtain aconcentrate rich in oxidized values. I

4. In the concentration by froth flotation of ores containing oxidizedbase metals, the method which comprises subjecting a pulp containingsuch ores to conditioning in the presence of an isopolyacid of tungsten,and thereafter subjecting the pulp to froth flotation to obtain aconcentrate'rich in oxidized values.

5. In the concentration by froth flotation of ores containing oxidizedbase metals, the method which comprises adding to an acid, neutral orslightly alkaline pulp containing such ores, a reagent chosen from thegroup consisting of stannic acid, tungstic acid, vanadicacid, germanicacid, molybdic acid and their salts, conditioning the thus treated pulp,and thereafter subjecting the pulp to froth flotation to obtain aconcentrate rich in oxidized values.

6. In the concentration by froth flotation of ores containing oxidizedbase metals, the method which comprises adding 'molybdic acid or a saltthereof to an acid, neutral or slightly alkaline pulp containing suchores, conditioning the thus treated pulp. and thereafter subjecting thepulp to froth flotation to obtain a concentrate rich in oxidized values.

7. In the concentration by froth flotation of ores containing oxidizedbase metals, the method which comprises adding stannic acid or a saltthereof to an acid, neutral or slightly alkaline pulp containing suchores, conditioning the thus treated pulp, and thereafter subjecting thepulp to froth flotation to obtain a concentrate rich in oxidized values.

8. In the concentration by froth flotation of ores containing oxidizedbase metals, the method which comprises adding tungstic acid or a saltthereof to an acid, neutral or slightly alkaline oanooma' 0mm.

